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Spinophorosaurus
Spinophorosaurus is a genus of sauropod dinosaur that lived in what is now Niger during the Middle Jurassic period. The first two specimens were excavated in the 2000s by German and Spanish teams under difficult conditions. The skeletons were brought to Europe and digitally replicated (it is the first sauropod to have its skeleton 3D printed) but were to be returned to Niger in the future. Together, the two specimens represented most of the skeleton of the genus, and one of the most completely known basal sauropods of its time and place. The first skeleton was made the holotype specimen of the new genus and species Spinophorosaurus nigerensis in 2009; the generic name ("spine-bearing lizard") refers to its spiked osteoderms, while the specific name refers to where it was found. A juvenile sauropod from the same area was later assigned to the genus. The subadult holotype specimen is estimated to have been around 13 metres (43 ft) in length, whereas the paratype was about 14 metres (46 ft). The shoulder height reached by these individuals was estimated at around 4 metres (13 ft); the weight at about 7 metric tons (7.7 short tons). The braincase was short, deep, and broad, and the neuroanatomy was in some ways intermediate between that of basal sauropodomorphs and the more derived neosauropods. The teeth were spatulate (spoon shaped) and had large spaced denticles at the top of the crown, an ancestral feature in sauropods. The neck of Spinophorosaurus is one of the most completely known among sauropods, containing 13 vertebrae. The dorsal vertebrae had multiple small, air-filled internal chambers, a feature typical of later, more advanced sauropods. The tail was powered by strong musculature and had a rear section that was rather rigid due to long and overlapping chevron bones. Osteoderms bearing spikes appear to have been placed on the tail tip in two pairs (the source of the generic name); a similar feature is seen in the related Shunosaurus. Spinophorosaurus has either been classified as a very basal sauropod outside Eusauropoda, or included in that group. The anatomy, age, and location of Spinophorosaurus indicate that important developments in sauropod evolution may have occurred in North Africa, possibly controlled by climatic zones and plant biogeography. Features of the vestibular apparatus indicate that vision and coordinated eye, head, and neck movements were important in Spinophorosaurus. Due to the completeness of Spinophorosaurus, 3D models have been made of the skeleton, and used to test its range of motion. One study suggests it may have been a high browser, and another examined possible mating postures. The spikes on the tail may have been used for defence. Sutures between the neural arches with the centra of the vertebrae were more complex in the front part of the trunk of Spinophorosaurus, since stresses were probably greatest in that region. Spinophorosaurus is known from the Irhazer Shale, a geological formation thought to be Middle Jurassic in age. It was formed by deposits from rivers and lakes in a great river-valley system. Category:Animals Category:Dinosaurs Category:Species